Gasification of carbonaceous solids to hydrogen-rich gas and fuel gas



' J. c. KALBAcH GASIFICAT ION 0F CARBONACEOUS SOLIDS T0 HYDROGEN-RICHGAS AND FUEL GAS Filed April 8, 1949 Aug. 31, i954 INVENTOR.

/WATTOKMEYS Patented Aug. 31, 1954 GASHICATION OlF CARBONACEOUS SOLIDST() HYDRQGEN-RICH GAS AND FUEL GAS .lohn C. Kalbach, New York, N. Y.,assigner to Hydrocarbon Research, Inc., New York, N. Y., a corporationof New Jersey Application April 8, 1949, Serial No. 86,334

6 Claims.

This invention relates to a process for the gasification of solidcarbonaceous materials. The process of this invention is particularlyapplicable to the gasication of coals including anthracite, bituminouscoals and lignite, to produce a gas rich in hydrogen and a fuel gas ofrelatively high heating value.

Two desiderata have been stated for an ideal gasification process. Inaddition to yielding a usable city gas at high thermal emciency, itshould be capable of modication to produce a hydrogen-rich gas, such asgas suitable for synthesis of hydrocarbons, and a fuel gas of highheating value suitable for transportation considerable distances bypipeline. Numerous processes have been devised for the gasiiication ofcarbonaceous materials for the production of hydrogen, Fischer-Tropschsynthesis feed gas, city gas, and the like, but most of these processessuffer from iniiexibility and many are either too complex or tooexpensive in operation to find practical application.

The process of the present invention is capable of producing ahydrogen-rich synthesis gas having, for example, a hydrogen-to-carbonmonoxide ratio of approximately 2:1 and a pipeline gas having a heatingvalue of 800 to 1000 B. t. u.s per cubic foot. This process is capableof converting 80 per cent of the heating value of the feed coal to thedesired gaseous products after supplying all the power required foroperation.

An important object of this invention is to provide a novel process forthe gasication of solid carbonaceous materials to produce both ahydrogen-rich gas and a fuel gas of high heating value.

Another object is to provide such a process which is adaptable toproduction of various types of gases from various solid carbonaceousfuels.

Still another object of this invention is to provide an improved processfor the production of a hydrogen-rich gas from a solid carbonaceousfuel.

A further obj ect is to provide an improved process for the productionof fuel gases of high heating value from a solid carbonaceous fuel.

Other objects and advantages will be apparent from the followingdetailed description taken in connection with the accompanying drawing.

The drawing is a diagrammatic View illustrating a preferred example ofthe process of the present invention as applied to the gasification ofcoal to produce synthesis gas and pipeline gas simultaneously.

The present invention is applicable to the gasication of solidcarbonaceous material yin the form of particles of relatively smallsizes such as slack coal, coke breeze, and the like. The gasiiication ispreferably carried out in a uid bed type reactor, particularly where thefeed material has a tendency to agglomerate or cake. Agglomerating coalsor caking coals may be successfully used in the process of the presentinvention.

In accordance with this invention, the carbonaceous feed material isgasified by reaction with oxygen and steam, the tars, oils and waterseparated from the resulting product gas and the gas separated intofractions, one of which is rich in hydrogen and -another rich inhyrocarbons. The separation may be carried out by low temperaturefractionation of the Linde-Frankl type.

With reference to the drawing, solid carbonaceous material in particleform, for example, coal, is supplied to a feed hopper II from which itis fed into a stream of carrier gas in line II. The carrier gas streammay be a gas produced in the system or a selected fraction of such gasand lnay comprise hydrocarbons, carbon monoxide, hydrogen, or otherinnocuous gas, e. g., a recycle gas stream, and is supplied to line IIat a rate sufficient to entrain the particles of coal. The coal is fedthrough lines Il and 2| into a carbonization zone I2 wherein it isfluidized and distilled by the action of hot gases passing upwardlythrough a bed of the coal particles. The coal particles are preferablyless than 40 to 60 mesh in size, 40 to 50 per cent thereof being 200mesh or smaller. The iiuidizing gas stream is introduced at a rate suchthat its rate of ilovv in the carbonization zone I2 is on the order ofabout 0.5 to about 3.0 feet per second.

The hot gases, and in some cases the exothermic energy of conversionsoccurring in the carbonzation zone I2, distill volatilizableconstituents from the coal, the fluidizing action of the gases insuringexcellent contact between the gas and the coal particles. The hot gasesare obtained from a gasification zone in which solid carbonaceousparticles are reacted with oxygen and steam under conditions such that amixture of hydrogen and carbon monoxide is produced.

The temperature of the carbonization zone is maintained within the rangeof from about 1,000 to about 1,500 F. the pressure, within the range offrom about to about 800 pounds per square inch gauge. The temperaturemay be controlled by a cooling coil I3 disposed in the iluidized bed ofcarbonaceous particles in the carbonization zone. Alternatively, thetemperature may be controlled by circulating the solids betweencarbonization Zone I2 and a cooler connected therewith. Under theseconditions, particularly at the higher pressures, some hydrogenaton andmethane formation taires place within the carbonization zone. Methanemay be formed by the interaction of hydrogen and carbon monoxide. Thecarbonizaticn zone may be operated under conditions either more or lessfavorable to the production of methane, depending upon the requirementsfor fuel gas from the system. formation is desirable for the productionof high heating value fuel gas but undesirable where synthesis gas isthe desired product.

It is apparent that the process cf this invention, which provides asource of both fuel gas and synthesis gas, is an improvement over thoseprocesses of the prior art wherein one of these product gases isproduced and wherein neither can be produced at high thermal eniciency.

The gases from the carbonizaticn zone i2 are discharged through line I4into a separator I5 to effect removal of solid materials from the gasesproduced in the gasification apparatus. The solids removed from the gasstream are passed through line i5 into either or both of lines I'F andI6. Normally, a portion of the solids or char from line I6 are passedinto line I8 to supply the gasification zone and the remainder recycledthrough lines I'I and 2| to the carbonization zone. A stream of asuitable carrier gas is introduced through line I'I at a rate of iiowsuiiicient to entrain the solids from line I6 and transport them intoline 2|. The rate of recycle of solids to the carbonization zone dependsupon several operating factors like temperature control and the gasvelocity in said zone. Generally, Where the coal is of the coking orcaking type, it is desirable to recirculate about 10 parts of char perpart of coal fed to the process to prevent agglomeration of coalparticles in the carbonization zone.

Oxygen and steam are introduced through line I8 for reaction with thesolid particles from line I 6. The particles of solid from line i6 areadmixed with oxygen and steam in line I8 and passed into reaction zone20. Preferably, the oxygen admixed with the steam is in the form of anoxygen concentrate containing at least 95 per cent oxygen by volume.Oxygen produced by conventional processes, such as the Linde-Franklprocess, is suitable for the gasification. The steam and oxygen reactwith the solid particles in the gasification zone to produce a mixtureof hydrogen and carbon monoxide, as Well as carbon dioxide and watervapor depending on the residence time of the gases in the gasificationzone.

Preferably the gasification reaction is conducted at a temperature inthe range of from about 1400 F. to about 2100 F. and at a pressurecorresponding to that in the carbonization zone; of course, thegasification temperature is not lower than the carbonizationtemperature.

The gases produced in the gasification zone are discarged through line2l into the carbonization zone I 2. Solids are Withdrawn from thegasification zone to line 22. These solids may be used as fuel or may bepassed to a separate gasification unit for complete carbon cleanup,leaving ash and slag as a residue. Withdrawal of a stream of solidsthrough line 22 provides a method for eliminating ash from thegasification system.

The products from the gasification apparatus, after separation of solidstherefrom, are passed through line 24 into a separator 25 wherein tar,

Methane oil and water, together with any entrained solids passingthrough separator I5, are removed from the gases. The resulting gasstream is then passed through line 2 into a separation unit 28 wherein ahydrogen-rich fraction comprising chiey carbon monoxide and hydrogen, isseparated from a fuel gas fraction comprising chiefly methane. Thehydrogen-rich stream is discharged from the separation unit through line29 and fuel gas through line 30. Preferably, the separation unit 28 isof the low temperature type wherein at least a portion of the gas streamis condensed to liquid form and fractionally distilled under pressure.The gasification apparatus may be operated at a pressure such thatlittle. if any, additional compression is required for liquefaction toeffect low temperature fractionation.

A gasification and carbonization unit of the type described herein isoperated with coking coal at a pressure of 600 pounds per square inchgauge. A temperature of about 1200 F. is maintained in the carbonizationzone by cooling coils which are used for the generation of steam. About10 parts of coke per part of fresh feed is recycled to the carbonizationzone to prevent agglomeration of the fresh coal feed. A portion of theproduct gas is returned to the carbonization zone at 900 F. as a carriergas for the fresh coal and recycled coke. rIhe gasication zone isoperated at 1600 F. The gases have a residence time of about 18 secondsin the gasification zone. All of the gas from the gasication zone ispassed into the carbonization zone. Approximately 1515 pounds of oxygenand 2170 pounds of steam are used per ton of coal.

The product gases are withdrawn from the carbonization zone, cooled,cleaned and separated by low temperature fractional distillation into ahydrogen-rich gas suitable as synthesis gas feed and a pipeline gas ofhigh heating value. The yields per ton of coal are approximately asfollows:

24,400 cubic feet of synthesis gas of the following analysis:

Per cent by volume Hydrogen 66 Carbon monoxide 33 Nitrogen l 13,100cubic feet of pipeline gas having a heating value of 914 B. t. u.s percubic foot and the following analysis:

Per cent by volume Carbon Monoxide 19.6 Methane 77.8 Illuminants 2.6

In addition, about 200 pounds of tar and light oil having a heatingvalue of 3,300,000 B. t. u.s, are recovered. About per cent of theheating value of the coal is recovered in the form of the variousproducts.

In another modification of the operation of the present process, thecarbonization zone is operated at 1250 F. and the gasification zone at1650 F. The contact or residence time of the gases in the gasificationzone is limited to about 4 seconds so that the water gas shift reactionis substantially complete but the producer gas reaction is incomplete.About 745 pounds of oxygen and 2760 pounds of steam are used per ton ofcoal. Under these conditions, the following yields are obtained per tonof coal:

25,600 cubic feet of synthesis gas of the following analysis:

Per cent by volume Hydrogen 65.8

Carbon monoxide 32.9 Nitrogen 1.3

13,100 cubic feet of fuel gas having a heating value of 1,022 B. t. u.sper cubic foot and the following analysis:

Per cent by volume Carbon monoxide 3.2 Methane 94.5 Illumin ants 2.3

(CoH-C zoo) takes place. This reaction may be eiectively limited bymaintaining a contact time, or reaction time. of less than about 5seconds. It will be noted that by so limiting the reaction time, asdetermined by rate of throughput, the oxygen requirement for the secondmodification is less than half that of the former; comparable yields ofsynthesis gas are obtained, the heating value of the fuel gas isconsiderably improved, and the efficiency of the operation measurablyincreased. To obtain these important advantages of my invention thecontact time between reactant gas and carbon in the reaction zone islimited to less than 5 seconds. This may be accomplished by iiow of thereactant gases through the gasication zone at a rate such that thecontact time therein is less than 5 seconds. 'Ihe preferred range ofcontact time is from 2 to 5 seconds.

From the foregoing specific examples illustrating the operation of thepresent invention, it will be evident that the process of this inventionis adaptable to varying product requirements. The ilexibility of theprocess is an important advantage over processes of the prior art whichproduce only a single product.

In carrying out the process of the present invention, it has been founddesirable to operate the gasification zone with an oxygen feed rate offrom about 0.25 to about 1.0 pound and a steam feed rate of from about1.5 to about 1.0 pounds per pound of carbon reacted. In the preferredcase, as illustrated by the second example, where the contact time isfrom about 2 to about 5 seconds, the oxygen feed rate is within therange of from about 0.25 to about 0.50 pound and the steam feed rate iswithin the range of from about 1.50 to about 1.25 pounds per pound ofcarbon reacted. It will be evident from the foregoing examples andexplanation that as' the contact time is decreased, the oxygenrequirement is decreased and the steam requirement is increased.

Obviously many modications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and, therefore, only such limitations should beimposed as are indicated in the appended claims.

I claim:

1. A process for the gasication of a solid carbonaceous materialcontaining volatilizable constituents which comprises introducing saidsolid carbonaceous material into a carbonization zone into directcontact with hot gases comprising carbon monoxide and hydrogen at atemperature within the range of from 1,000 F. to 1,500" F. and apressure within the range of 100 to 800 pounds per square inch gaugewhereby Volatiliz- 6 able constituents are volatilized and methane isformed; introducing the resulting carbonaceous residue from thecarbonization zone into a gasication zone, reacting said residue with amixture of oxygen and steam at a temperature within the range of from1,400o F. to 2,100 F., to produce carbon monoxide and hydrogen asprincipal reaction products; passing the resulting gases from thegasification Zone to the carbonization zone as the source of hot gases;discharging product gases from the carbonization zone; separatingentrained solids and readily liquefiable constituents therefrom; andsubjecting the residual gaseous product comprising carbon monoxide,hydrogen and methane to liquefaction and fractional distillation toobtain a methane-rich fuel gas and a synthesis gas comprising carbonmonoxide and hydrogen in substantial proportions adapted forFischer-Tropsch synthesis.

2. A process as dened in claim 1 wherein said solid carbonaceousmaterial is coal.

3. A process as dened in claim l wherein a fluidized bed of particles ofsolid carbonaceous material is maintained in each of said carbonizationand gasification zones.

4. A process for the gasification of a solid carbonaceous materialcontaining volatilizable constituents which comprises introducing saidsolid carbonaceous material into a carbonization zone into directcontact with hot gases comprising carbon monoxide and hydrogen at atemperature within the range of from 1,000 F. to l,500 F.

and a pressure within the range of to 800 pounds per square inch gaugewhereby volatilizable constituents are Volatilized and methane isformed; introducing resulting carbonaceous residue from thecarbonization zone into a gasification zone; reacting said residue witha mixture of oxygen and steam in said gasification zone at a temperaturewithin the range of from about 1,400 F. to about 2,100 F. with a time ofcontact between said gases and said carbonaceous residue within therange of from about 2 to about 5 seconds to produce carbon monoxide andhydrogen as the principal reaction products; passing the resulting gasesfrom the gasification zone to the carbonization Zone as the source ofsaid hot gases; discharging product gases from the carbonization zone;separating entrained solids and readily liquefiable constituentstherefrom; and subjecting the residual gaseous product comprising carbonmonoxide, hydrogen, and methane to liquefaction and fractionaldistillation to obtain a methane-rich fuel gas and a synthesis gascomprising carbon monoxide and hydrogen in substantial proportionsadapted for Fischer-Tropsch synthesis.

5. A process for the lgasification of a solid carbonaceous materialcontaining volatilizable constituents which comprises introducing saidsolid carbonaceous material into a carbonization zone into directcontact with hot gases comprising carbon monoxide and hydrogen at atemperature within the range of 1,000 F. to 1,500 F. and a pressurewithin the range of 100 to 800 pounds per square inch gauge wherebyvolatilizable constituents are volatilized and methane is formed;introducing resulting carbonaceous residue from the carbonization zoneinto a gasication zone; effecting reaction of the carbonaceous residuein said gasification zone by contacting said residue with a mixture ofoxygen and steam wherein from about 0.25 to about 0.5 pound of oxygenand from about 1.5 to about 1.25 pounds of steam are supplied per poundof carbon reacted; maintaining'the temperature of -said'gasication zoneWithin the range of 1,400 F. to 2,100" Ffthereby and readily liqueableconstituents therefrom;

and subjecting the residual gaseous product coinprising carbon monoxide,hydrogen and methane to liquefaction and fractional distillation toobtain a methane-rich fuel gas and a synthesis gas comprising carbonmonoxide and hydrogen in substantial proportions adapted for Fischer-Tropsch synthesis.

6. A process for the gasification of a solid carbonaceeous materialcontaining volatilisable constituents which comprises introducing saidsolid carbonaceous material into a carbonization zone into directContact with hot gases comprising carbon monoxide and hydrogen at atemperature within the range of 1,000 F. to 1,500 F. and a pressurewithin the range of 100 to 800 pounds per square inch gauge wherebyvolatilizable constituents are volatilized and methane is formed;introducing resulting carbonaceous residue from the carbonization zoneinto a gasification zone; eecting reaction of the carbonaceous residuein said gasication zone by contacting said residue with a mixture ofoxygen and steam wherein from about 0.25 to about 0.5 pound of oxygenand from about 1.5 to about 1.25 pounds of steam are supplied per poundof carbon reacted; supyplying said mixture of oxygen and steam at a ratesuch that a contact time of from 2 to 5 seconds is obtained; maintainingthe temperature of said gasification zone Within the range of 1,400 F.to 2,l00 F. thereby producing carbon monoxide and hydrogen; passing theresulting gases from the gasication zone to the carbonization Zone asthe source of said hot gases; discharging product gases from thecarbonization zone; separating entrained solids and readily liqueableconstituents from said product gases; and subjecting the residualgaseous product cornprising carbon monoxide, hydrogen and methane toliquefaction and fractional distillation to obtain a methane-rich fuelgas and a synthesis gas comprising carbon monoxide and hydrogen insubstantial proportions adapted for Fischer- Tropsch synthesis.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,094,946 Hubmann Oct. 5, 1937 2,414,586 Egloi Jan. 21, 19472,503,265 Haynes Apr. 11, 1950 2,591,658 Haringhuizen Apr. l, 1952FOREIGN PATENTS Number Country Date 623,323 Germany Dec. 18, 1935503,158 Great Britain Apr. 3, 1939

1. A PROCESS FOR THE GASIFICATION OF A SOLID CARBONACEOUS MATERIALCONTAINING VOLATILIZABLE CONSTITUENTS WHICH COMPRISES INTRODUCING SAIDSOLID CARBONACEOUS MATERIAL INTO A CARBONIZATION ZONE INTO DIRECTCONTACT WITH HOT GASES COMPRISING CARBON MONOXIDE AND HYDROGEN AT ATEMPERATURE WITHIN THE RANGE OF FROM 1,000* F. TO 1,500* F. AND APRESSURE WITHIN THE RANGE OF 100 TO 800 POUNDS PER SQUARE INCH GAUGEWHEREBY VOLATILIZABLE CONSTITUENTS ARE VOLATILIZED AND METHANE ISFORMED; INTRODUCING THE RESULTING CARBONACEOUS RESIDUE FROM THECARBONIZATION ZONE INTO A GASIFICATION ZONE, REACTING SAID RESIDUE WITHA MIXTURE OF OXYGEN AND STEAM AT A TEMPERATURE WITHIN THE RANGE OF FROM1,400* F. TO 2,100* F., TO PRODUCE CARBON MONOXIDE AND HYDROGEN ASPRINCIPAL REACTION PRODUCTS; PASSING THE RESULTING GASES FROM THEGASIFICATION ZONE TO THE CARBONIZATION ZONE AS THE SOURCE OF HOT GASES;DISCHARGING PRODUCT GASES FROM THE CARBONIZATION ZONE; SEPARATINGENTRAINED SOLIDS AND READILY LIQUEFIABLE CONSTITUENTS THEREFROM; ANDSUBJECTING THE RESIDUAL GASEOUS PRODUCT COMPRISING CARBON MONOXIDE,HYDROGEN AND METHANE TO LIQUEFACTION AND FRACTIONAL DISTILLATION TOOBTAIN A METHANE-RICH FUEL GAS AND SYNTHESIS GAS COMPRISING CARBONMONOXIDE AND HYDROGEN IN SUBSTANTIAL PROPORTIONS ADAPTED FORFISCHER-TROPSCH SYNTHESIS.